|While recently making a pair of velour pants with a drawstring waist, I was at odds trying to decide what to use for a drawstring. I ended up using polyester twill tape, but wasn't completely satisfied with it. Then I looked at a pair of pants I had... the ends of the drawstring had the plastic shoelace type of thing on it. Then it hit me... use shoelaces for drawstrings!
You can buy shoelaces in lengths from 27 to 72 inches. http://www.lacesforless.com sells them in all lengths and has a large variety of colors.